Hyomen Kagaku
Online ISSN : 1881-4743
Print ISSN : 0388-5321
ISSN-L : 0388-5321
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Volume 29, Issue 3
Displaying 1-12 of 12 articles from this issue
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Preface
Special Issue on Diamond Surface and Interface Research
  • p-type Surface Accumulation Layer of Hydrogen Terminated Diamond
    Hiroshi KAWARADA, Kazuyuki HIRAMA, Daisuke OGIWARA
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 144-150
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.144
    JOURNAL FREE ACCESS
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    The discovery process and the mechanism of p-type surface layer accumulation of hydrogen terminated diamond surfaces have been reviewed from the point of surface characterization and carrier formation near the subsurface. Since diamond is an insulating material, the surface density is as high as the order of 1013 cm−2 that is enough for high performance field effect transistors to be realized. The surface dipole formed by hydrogen-carbon bonds has a crucial role for the surface band structure of diamond. Also important is several types of negatively charged adsorbates necessary for charge neutrality condition and hole accumulation. New models for carrier emergence such as a transfer doping model have been discussed.
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  • Total Photoelectron Emission Yield Spectroscopy on Diamond Surfaces
    Daisuke TAKEUCHI, Satoshi YAMASAKI
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 151-158
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.151
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    Diamond has unique physical and chemical properties such as the highest thermal conductivity. Especially, the negative electron affinity (NEA), where the conduction band minimum is higher than the vacuum level, is highlighted for a long time as to be one of the best candidates for the electron emitters. We have developed growth techniques of high quality diamond films, and total photoelectron emission yield spectroscopy (TPYS) equipment to be able to investigate NEA on diamond. Now it is possible to determine NEA quantitatively, and characterize electronic properties of surface and bulk of diamond by means of NEA. According to these results, we find that free-exciton derived electron emission plays an important role in electron emission from diamond with the NEA surface, and finally realizes a NEA electron emitter with diamond p-n junction diodes. The diamond semiconductor, that makes it possible to study “excitonics” at room temperature, will be one of the most exciting materials for the next surface science.
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  • Gate Metal Interface on Hydrogen-terminated Diamond FETs
    Makoto KASU, Kenji UEDA, Hiroyuki KAGESHIMA
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 159-163
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.159
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    Hydrogen surface termination is widely used as a p-type doping in diamond semiconductors, but the p-type conduction mechanism is still controversial. In this study, we found an energy barrier for holes between the gate and the two-dimensional hole channel on the hydrogen-terminated diamond surface from FET characteristics. Separately we confirmed an interfacial layer between the gate metal layer and hydrogen-terminated diamond surface from cross-sectional transmission electron microscopic observation. We conclude that during metal evaporation on hydrogen-terminated diamond surface, metal atoms diffuse through point defects in the subsurface layer, and eventually the interfacial layer forms there.
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  • Applications of Boron-doped Diamond Electrodes to Electrochemical Sensors
    Yasuaki EINAGA
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 164-172
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.164
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    Conductive boron-doped diamond (BDD) electrodes are very attractive electrode materials because of their superior electrochemical properties such as wide potential window, low background current, chemical inertness, and mechanical durability. We have studied the application of diamond electrodes as electrochemical sensors for the detection of several types of biochemical species or environmental pollutants. For example, free chlorine, metals (Zn, etc), and proteins including cancer markers could be detected by using the diamond electrodes with very high sensitivity and high stability. Furthermore, modified diamond electrodes such as ion-implanted diamond electrodes and diamond electrodes with micro-meter size were also prepared in order to improve the electrochemical properties. Here, several examples for electrochemical applications by using the boron-doped diamond electrodes were introduced.
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  • Surface Electronic Energy States of Phosphorous-Doped CVD Diamonds and Electron Emission
    Shozo KONO
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 173-180
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.173
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    Phosphorous (P)-doped CVD diamonds are expected to be good n-type semiconductor diamonds. However, the resistivity of P-doped intrinsic diamonds is very high due to a large ionization energy of impurity phosphorus. When phosphorus is doped in a large amount (≥∼1020cm−3), the resistivity reduces with a pseudo-n-type conductivity at temperatures above 400 K. These intrinsic n-type and pseudo-n-type P-doped diamond single crystal surfaces have been studied recently by electron spectroscopic methods. The surface electronic energy states of both intrinsic n-type and pseudo-n-type diamond surfaces have been examined by electron spectroscopic methods. The mechanism of field emission from the pseudo-n-type diamond surface has been elucidated.
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  • Photochemical Modification of Diamond and Related Materials with Fluorine Functionalities
    Takako NAKAMURA
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 181-186
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.181
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    Photolysis of perfluoroazooctane with diamond and related materials, such as diamond powders, films, diamond-like carbon (DLC) and nanodiamond films, led to a chemical modification of the surface to introduce perfluorooctyl functional groups, confirmed by means of FT-IR, XPS, Raman and TOF-SIMS measurements. The diamond and related materials modified with fluorine moieties showed an improvement of frictional property and a reduction of surface energy evaluated by contact angle to water, compared with pristine diamond, DLC and nanodiamond films. The results on the values of water contact angle depending on irradiation time are consistent with those of F/C ratio of fluorinated diamond and related materials by monitoring with XPS.
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  • Development of a Diamond Electron Source for Electron Optics Instruments and Evaluation of Energy Spread using the Source
    Akihiko UEDA, Yoshiyuki YAMAMOTO, Yoshiki NISHIBAYASHI, Takahiro IMAI
    Article type: Current Topic
    2008 Volume 29 Issue 3 Pages 187-192
    Published: March 10, 2008
    Released on J-STAGE: March 23, 2008
    DOIhttps://doi.org/10.1380/jsssj.29.187
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    Diamond that shows low or negative electron affinity has good electron emission properties. The authors are developing a diamond electron source, which is suited for electron optics instruments such as electron beam exposure systems and electron microscopes. As a result of thermionic emission evaluations, an electron emission current of practical level (116 μA at 600oC) was obtained. The energy spread of an electron beam generated by thermionic emission was measured as 0.23 eV (FWHM), the value of which was lower than those of a LaB6 cathode and a ZrO/W cathode measured together. The result of field emission evaluations, a practical beam current (459 pA) and stability (6%rms for 10 h) for scanning electron microscope (SEM) was obtained. The energy spread of over 200 pA of a high current electron beam generated by field emission was about the same as that of a tungsten field emission cathode. It was found that an unprecedentedly high current and high convergence electron source can be made by using diamond.
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